The hip is a ball and socket joint which in its normal state glides freely. Various disease processes commonly attack the surfaces of this joint, causing those surfaces to become rough, thereby increasing the friction load and causing pain as well as limited motion. A common practice is to replace severely diseased hip joints with artificial means. The socket portion is replaced with an artificial acetabular cup. The normal human acetabulum, or hip socket, is quite thin, being approximately 1/8 inch in thickness at the base of the socket, but quite substantial around the peripheral margins. When either a plastic or metal backed cup is placed in the acetabulum, it is first necessary for the surgeon to ream the socket to fit the artificial implant. This requires removing bone from an area where there was very little to start with as concerns the central portion of the socket. If an artificial hip socket has to be removed because of malposition, wear or infection, the only available methods at the present time are to either pry out the implant with various forms of chisels or cut the implant into small pieces and again pry them away from the thin pelvic wall. This surgery is performed deep in the hip joint with limited exposure to surgical instruments, and the operation is frequently bloody; therefore, limiting the surgeon's vision.
Patents related to the subject matter are: U.S. Pat. Nos. 3,752,161; 4,124,026; 4,271,849; 4,355,931; and Russian Patent No. 829,109. The basic standard rotary impact wrench used to remove wheel lug bolts on cars contains a rotary impact mechanism used in subject surgical rotary impact tool to provide repeated rotary impact motion. These wrenches are used throughout the country and are manufactured and sold by numerous companies, some of which are Chicago Pneumatic Co.; Ingersoll Rand Corp.; Florida Pneumatic Co.; and NAPA.